The invention relates to a method of uninterrupted operation of a current supply installation and apparatus for the method.
In such an installation, a storage battery charger is driven, which rectifies the operating voltage coming from an AC current supply or a generator, and which via a transformer transforms it to a suitable voltage for charging a battery and carrying a load. If there is a break in voltage, the load is carried by the battery. The battery voltage is thus always the same as the load voltage. Nearly always, the load has a limited voltage range, within which the ingoing voltage must be kept. Battery dimensioning is thus dependent to a great degree on the permitted voltage range of the load. The battery charger must be of the so-called constant voltage type.
In order to fully charge the battery, a certain least voltage per cell is required. The number of cells in the battery is therefore determined by the greatest permitted voltage of the load divided by this least charging voltage per cell. The lowest final cell voltage which can be tolerated, when the battery is carrying the load, will be equal to the lowest permitted load voltage divided by the number of cells in the battery.
Even with a relatively generously defined range for the load voltage, relatively high permitted final voltages per cell are often arrived at in this kind of dimensioning. A high final voltage combined with operating times, e.g. in the range of 10-60 minutes, for the battery, give poor utilization of the energy stored in the battery.
A complete current supply installation of a kind known up to now is generally constructed in the following way. An incoming AC voltage is rectified, smoothed and chopped into square wave form, e.g. in a transistor. The square wave voltage is then transformed to a suitable voltage for charging and operation, and is once again rectified to remove the square wave form, filtered and used for charging the battery and carrying the load. Regulation of the output voltage is obtained by pulse width, amplitude or frequency being varied by a control unit, which senses the output signal and regulates the square wave generator. If the incoming alternating voltage is interrupted, the load is fed directly with the voltage from the battery.